1. Field of the Invention
The invention relates to chemical vapor deposition ("CVD") reactors. More particularly, the invention relates to an improved apparatus and method for introducing gases into a process chamber of a CVD reactor.
2. Description of Related Art
The manufacture of semiconductor devices relies substantially upon the ability to deposit materials on a semiconductor substrate in a highly controllable manner. Not only must the physical layout of the various active and passive layers be highly controlled, but the uniformity and repeatability of results from chip to chip and wafer to wafer must be reliable. Failure to achieve such consistent, reliable and controllable results translates into problems ranging from low manufacturing yields to products that are partially or wholly inoperable.
One known method of semiconductor processing technology involves chemical vapor deposition ("CVD"). According to this method, the semiconductor substrate is maintained in a heated process chamber into which select gases are introduced. Within the chamber, which may be held at atmosphere or evacuated to a vacuum, the gases chemically react to deposit material on the substrate. This process is carried out through apparatus commonly referred to as CVD reactors. One example of such a reactor is the subject of U.S. Pat. No. 4,632,058, issued Dec. 30, 1986 to Dixon et al. The '058 patent is incorporated herein by reference.
As described in the '058 patent, a variety of efforts have been expended to control factors involved in the deposition process, e.g., layer thickness, resistivity, dopant concentration, etc. These efforts have involved efforts to alter factors such as the physical dimensions of the process chamber, the table or susceptor on which the substrate material is positioned, the temperature and manner of heating of the chamber. Also described in that patent are efforts directed to the shape of the nozzles, or wands, used to deliver the selected gases to the interior of the process chamber.
While such efforts have, to date, enjoyed some degree of success, further improvement in process technology continued to be desired. For example, the '058 patent is directed to establishing a precise relationship in the ratio of height of the process chamber to diameter of the susceptor table. However, both structures are relatively costly and cannot be altered easily. Thus, the requirement of adhering to this ratio meant that other reactors with different ratios did not operate as efficiently as possible, and they could not easily be modified.
Accordingly, a need existed in the industry to provide a better, cleaner and more efficient way to control semiconductor processing in CVD reactors.